Analyzers are used for decentralized determination of a number of parameters in whole blood. Such an analyzer may be, for instance, a portable analyzer for determining POC (Point of Care) parameters, i.e. blood gases (O2, CO2, pH), electrolytes (K+, Na+, Ca++, Cl−), metabolites (glucose and lactate), haematocrit, haemoglobin parameters (tHb, SO2, etc.) and bilirubin. Although such known analyzers are suitable for their intended purposes, further improvements are desired to address inherent deficiencies which detract from their utility.
For example, one problem to be solved concerns a way of connecting a plurality of reagent bags to the analyzer, such that all fluids, i.e. the sample (e.g. blood), which may be taken from diverse sample containers, external quality control (QC) fluids, and functional fluids present in the reagent bags of the reagent cartridge, such as calibrating, QC, rinsing, disinfecting and cleansing fluids, enter into the analyzer via a single input element (e.g. an input needle).
The partly tonometered functional fluids are contained in reagent bags (e.g. heat-sealed laminated aluminium bags). In known applications the reagent bags are closed prior to use in the analyzer with a septum or a valve (bag valve), which is irreversibly opened when the bag is inserted into the analyzer, releasing the bag's content.
It must be ensured that no cross-contamination of the sample content to be measured, or of calibrating and QC-fluids will occur. Furthermore it must be guaranteed that the composition of the gas mixture contained in the tonometered fluids of the bags or tubes will remain constant during operation but also during longer standby phases.
In this context there is known from DE 35 02 546 C2 an analyzer for measuring liquid and gaseous samples, in which the input element (e.g. a hollow needle) of the sample input assembly in its initial position seals the analyzer path against a docking element, which connects to tubes for the feeding of calibrating and standard media and to a valve-controlled air inlet. If the input element is tilted out of its initial position sample fluids from diverse sample containers can be entered. By providing air entry via a valve for separating the individual fluid samples or for drying of the sample path no other valves or shut-off devices are required. The shut-off valves of the individual reagent containers, which are separately exchangeable, are designed as simple blocking valves. U.S. Pat. No. 4,499,053 A discloses a similar type of analyzer.
It is disadvantageous that the lines from the reagent containers up to the shut-off valves and onwards from the shut-off valves to the fittings in the feeder line of the docking element cannot be emptied, or rather that these lines cannot be emptied without the fluid contained in the lines running back into the reagent containers and introducing air into the containers, thus changing the gas concentrations of the tonometered calibrating fluids.
Instead of the rigid reagent containers formerly used, flexible, heat-sealed bags made of laminated foil (e.g. aluminium foil) are preferred now.
The use of reagent bags contained in exchangeable reagent cartridges in blood analyzers has frequently been described in the patent literature, for example in U.S. Pat. No. 5,882,602A, U.S. Pat. No. 5,780,302 A and U.S. Pat. No. 6,872,297 B2.
U.S. Pat. No. 5,882,602 A for instance discloses a self-sealing valve in combination with a “flow fitting”. This means a septum made of an elastomer in the connecting element of the reagent bag, which on insertion into the analyzer is punctured by a needle. A bag connection described in U.S. Pat. No. 5,780,302 A is of similar kind.
The embodiment as shown in FIG. 1 of U.S. Pat. No. 6,872,297 B2 has an exchangeable reagent cartridge (disposable cartridge) with a plurality of reagent bags with calibrating and rinsing fluids (A, B, Rinse) whose connecting lines are led via a rotary valve and a “common rail” to the tiltable cannula of an input unit. From there the fluids are fed via another line into the measuring chamber and finally via a peristaltic pump into a waste container, which is also contained in the reagent cartridge. In a certain position of the rotary valve air can be fed into the common rail.
In the variant with a rotary valve of U.S. Pat. No. 6,872,297 A once again the connecting lines leading from the reagent bags to the rotary valve cannot be emptied without risking contamination of the bag content with air.
While it is known in the art to keep simple open/close valves of the bags closed during shelf storage of the reagent cartridge and to open them for the first time and irreversibly when the cartridge is inserted, the valves will stay open during the period of use of the cartridge and a separate rotary valve will route the fluids through the connecting lines. This arrangement will not permit emptying of the connecting lines. This is a disadvantage especially if the cartridge is used for a longer period of time.
During measurement operation of the analyzer the calibration and quality control fluids contained in the reagent cartridge must be transported contamination-free from the respective reagent bag to the measuring cell via a tube system, a common rail (see for instance DE 35 02 546 C2) or a rotary valve (see for instance U.S. Pat. No. 6,872,297 A) and a hollow needle.
If the apparatus is operational for a prolonged period of time, i.e., taking sample measurements or in standby state (typically between 1 and 8 hours), the gas permeability of the tube material of the individual lines (leading to the common rail or to the rotary valve) will cause significant changes in the gas concentrations of the calibrating or quality control fluids.